Coaxial guide catheter for interventional cardiology procedures

ABSTRACT

A coaxial guide catheter to be passed through guide catheter having a first lumen, for use with interventional cardiology devices that are insertable into a branch artery that branches off from a main artery. The coaxial guide catheter is extended through the lumen of the guide catheter and beyond the distal end of the guide catheter and inserted into the branch artery. The device assists in resisting axial and shear forces exerted by an interventional cardiology device passed through the second lumen and beyond the flexible distal tip portion that would otherwise tend to dislodge the guide catheter from the branch artery.

FIELD OF THE INVENTION

The present invention relates generally to catheters used ininterventional cardiology procedures. More particularly the presentinvention relates to methods and apparatus for increasing backup supportfor catheters inserted into the coronary arteries from the aorta.

BACKGROUND OF THE INVENTION

Interventional cardiology procedures often include inserting guidewiresor other instruments through catheters into coronary arteries thatbranch off from the aorta. For the purposes of this application, theterm “interventional cardiology devices” is to be understood to includebut not be limited to guidewires, balloon catheters, stents and stentcatheters. In coronary artery disease the coronary arteries may benarrowed or occluded by atherosclerotic plaques or other lesions. Theselesions may totally obstruct the lumen of the artery or may dramaticallynarrow the lumen of the artery. Narrowing is referred to as stenosis. Inorder to diagnose and treat obstructive coronary artery disease it iscommonly necessary to pass a guidewire or other instruments through andbeyond the occlusion or stenosis of the coronary artery.

In treating a stenosis, a guide catheter is inserted through the aortaand into the ostium of the coronary artery. This is sometimesaccomplished with the aid of a guidewire. A guide catheter is typicallyseated into the opening or ostium of the artery to be treated and aguidewire or other instrument is passed through the lumen of the guidecatheter and inserted into the artery beyond the occlusion or stenosis.Crossing tough lesions can create enough backward force to dislodge theguide catheter from the ostium of the artery being treated. This canmake it difficult or impossible for the interventional cardiologist totreat certain forms of coronary artery disease.

Prior attempts to provide support to the guiding catheter to preventbackward dislodgement from the coronary ostium (referred to as “backupsupport”) fall generally into four categories.

First are guiding catheters that, through a combination of shape andstiffness, are configured to draw backup support from engaging the wallof the aortic arch opposing the ostium of the coronary artery that isbeing accessed. Examples of this approach can be found in U.S. Pat. No.6,475,195 issued to Voda and U.S. Pat. No. 5,658,263 issued to Dang etal. These guiding catheters all share the common limitation that a guidecatheter stiff enough to provide adequate backup support is often toostiff to be safely inserted into the aorta without the possibility ofcausing damage to the aortic wall. In addition, attempts to deep seatthe guide catheter have been made but the rigid nature of the guidecatheter creates the risk that the guide catheter may damage thecoronary artery wall or that the guide catheter may occlude the coronaryartery and interfere with blood flow to the heart muscle.

Second are guiding catheters that include a retractable appendage. Theappendage in these catheters can be extended to engage the opposing wallof the aortic arch to provide backup support or the appendage may beplaced under tension to stiffen a bend in the catheter to provide backupsupport. Examples of this approach may be found in U.S. Pat. Nos.4,813,930 issued to Elliot; 5,098,412 issued to Shiu; and 6,860,876issued to Chen. These guiding catheters tend to be somewhat mechanicallycomplex and have not been widely adopted by practitioners.

Third are guide catheters that have a portion that seeks to expandlaterally to grip the interior wall of the ostium of the coronary arteryto provide a force acting in opposition to the backward forces createdwhen trying to maneuver a therapeutic device past a lesion or blockagein the coronary artery. These devices can include a balloon secured to aguidewire or a catheter or another device for expanding to grip thewalls of the coronary artery from within. Examples of this approach maybe found in U.S. Pat. Nos. 4,832,028 issued to Patel; 6,595,952 issuedto Forsberg; and U.S. Published Application No. 2005/0182437 by Bonnetteet al. Again, these devices tend to be mechanically complex and cancompletely occlude the coronary ostium thus stopping perfusion of thecoronary artery.

A fourth technique includes the placement of a smaller guide catheterwithin a larger guide catheter in order to provide added support for thecrossing of lesions or for the distal delivery of balloons and stents.This technique has been described in an article by Takahashi entitled“New Method to Increase a Backup Support of Six French Guiding CoronaryCatheter,” published in Catheterization and CardiovascularInterventions, 63:452-456 (2004). This technique is used in order toprovide a method of deep seating the guide catheter within the ostium ofthe coronary artery. Deep seating refers to inserting the catheter moredeeply into the ostium of the coronary artery than typically has beendone before. Unfortunately, deep seating by this technique with acommonly available guide catheter creates the risk that the relativelystiff, fixed curve, guide catheter will damage the coronary artery. Thisdamage may lead to dissection of the coronary artery when the catheteris advanced past the ostium.

Several other problems arise when using a standard guide catheter inthis catheter-in-a-catheter fashion. First, the inner catheters must besubstantially longer than the one hundred centimeter guide catheter.Second, a new hemostasis valve must be placed on the inner guidecatheter which prevents the larger guide catheter from being used forcontrast injections or pressure measurements. Third, the smaller guidecatheter still must be inserted into the coronary vessel with great caresince the smaller guide catheter has no tapered transition or dilator atits tip and does not run over a standard 0.014 inch guidewire.

Thus, the interventional cardiology art would benefit from theavailability of a system that would be deliverable through standardguide catheters for providing backup support by providing the ability toeffectively create deep seating in the ostium of the coronary artery.

SUMMARY OF THE INVENTION

The present invention is a coaxial guide catheter that is deliverablethrough standard guide catheters by utilizing a guidewire rail segmentto permit delivery without blocking use of the guide catheter. Thecoaxial guide catheter preferably includes a tapered inner catheter thatruns over a standard 0.014 inch coronary guidewire to allow atraumaticplacement within the coronary artery. This feature also allows removalof the tapered inner catheter after the coaxial guide catheter is inplace. The tapered inner catheter provides a gradual transition from thestandard 0.014 inch diameter guidewire to the diameter of the coaxialguide catheter which is typically five to eight French.

The coaxial guide catheter preferably can be delivered through commonlyexisting hemostatic valves used with guide catheters while stillallowing injections through the existing Y adapter. In addition, thecoaxial guide catheter preferably has an inner diameter that isappropriate for delivering standard coronary treatment devices after itis placed in the coronary artery.

In one embodiment, the coaxial guide catheter is made in at least threesizes corresponding to the internal capacity of 8 French, 7 French, and6 French guide catheters that are commonly used in interventionalcardiology procedures. An 8 French catheter has an internal diametergreater than or equal to 0.088 inches. A 7 French catheter has aninternal diameter greater than or equal to 0.078 inches. A 6 Frenchguide catheter has an internal diameter greater than or equal to 0.070inches. Thus, for three exemplary sizes the effective internal diameterof the coaxial guide catheter may be as follows. For a 7 French in 8French coaxial guide catheter the internal diameter should be greaterthan or equal to 0.078 inches. For a 6 French in 7 French coaxial guidecatheter the internal diameter should be greater than or equal to 0.070inches. For a 5 French in 6 French coaxial guide catheter the internaldiameter should be greater than or equal to 0.056 inches.

Interventional cardiology procedures are typically carried out underfluoroscopy or another x-ray or imaging technique. Therefore, oneembodiment of the coaxial guide catheter of the present inventionincludes a radiopaque marker at its distal tip to facilitate positioningand manipulation of the coaxial guide catheter.

The present invention generally includes the coaxial guide catheter anda tapered inner catheter. The coaxial guide catheter includes a tipportion, a reinforced portion, and a substantially rigid portion. Thecoaxial guide catheter will generally have an overall length ofpreferably approximately 125 cm, though this should not be consideredlimiting.

In one embodiment, the tip portion may include a soft tip and a markerband. The soft tip is tapered and may be formed from a low durometerpolymer or elastomer material such as polyether block amide polymer,(PEBA, Pebax®) the marker band may be formed from a platinum iridiumalloy sandwiched between the Pebax® that extends from the bump tip and aPTFE liner.

In one embodiment, the reinforced portion may be reinforced, preferablywith metallic fibers in a braided or coiled pattern. The braided orcoiled portion is lined by a PTFE liner and may be covered on itsexterior with Pebax®. The braided or coiled portion may extendapproximately 20 to 110 cm in length. In one exemplary embodiment, thebraided portion extends approximately 32 to 36 cm.

Preferably, the rigid portion may be advantageously formed from astainless steel or Nitinol tube. The rigid portion may be joined to thebraid or coil portion by welding. The rigid portion may include a cutoutportion and a full circumference portion. For example, the cutoutportion may include a section where about 45% of the circumference ofthe cylindrical tubular structure has been removed. The cutout portionmay also include a section where 75-90% of the circumference of thetubular structure has been removed. In one exemplary embodiment, theportion having approximately 45% removed may extend for approximately 75cm and the portion having 75-90% of the structure removed extends forabout 15 cm. The full circumference portion of the rigid portion istypically located at the most proximal end of the coaxial guidecatheter.

The rigid portion may include a plurality of radially oriented slits orother cuts in its distal portion to increase and control the flexibilityof the rigid portion

In an exemplary embodiment, the tapered inner catheter generallyincludes a tapered inner catheter tip and a cutout portion. The taperedinner catheter tip includes a tapered portion and a straight portion.The tapered portion is typically at the most distal end of the taperedinner catheter. Both the straight portion and the tapered portion arepierced by a lumen through which a guidewire may be passed.

The cutout portion supports a track passing along the concave sidethereof that continues from the lumen that passes through the straightportion and the tapered portion. The tapered inner catheter may alsohave a clip or snap attachment at its proximal end to releasably jointhe tapered inner catheter to the coaxial guide catheter.

In operation, the tapered inner catheter is inserted inside and throughthe coaxial guide catheter. The tapered inner catheter is positioned sothat the tapered inner catheter tip extends beyond the tip portion ofthe coaxial guide catheter. The coaxial guide catheter-tapered innercatheter combination may then be inserted into a blood vessel thatcommunicates with the aorta. The coaxial guide catheter-tapered innercatheter combination may be threaded over a preplaced 0.014 inchguidewire. The tapered inner catheter-coaxial guide catheter combinationis advanced up the aorta until the tapered inner catheter is passed intothe ostium of a coronary artery over the guidewire. Once the coaxialguide catheter-tapered inner catheter combination has been insertedsufficiently into the ostium of the coronary artery to achieve deepseating the tapered inner catheter may be removed. During this entireprocess at least part of the coaxial guide catheter-tapered innercatheter combination is located inside of the guide catheter.

Once the tapered inner catheter is removed a cardiac treatment device,such as a guidewire, balloon or stent, may be passed through the coaxialguide catheter within the guide catheter and into the coronary artery.As described below, the presence of the coaxial guide catheter providesadditional backup support to make it less likely that the coaxial guidecatheter guide catheter combination will be dislodged from the ostium ofthe coronary artery while directing the coronary therapeutic device pasta tough lesion such as a stenosis or a chronic arterial occlusion.

A guide catheter inserted into the ostium of a branch artery where itbranches off from a larger artery is subject to force vectors that tendto dislodge the distal end of the guide catheter from the ostium of thebranch artery when a physician attempts to direct a guidewire or otherinterventional cardiology device past an occlusive or stenotic lesion inthe branch artery. This discussion will refer to a guide wire but it isto be understood that similar principles apply to other interventionalcardiology devices including balloon catheters and stent catheters.

One of the forces that acts on the guide catheter is an axial forcesubstantially along the axis of the branch artery and the portion of theguide catheter that is seated in the ostium. This force vector is areactive force created by the pushing back of the guide wire against theguide catheter as the physician tries to force the guidewire through orpast the lesion. It tends to push the distal end of the catheter out ofthe ostium in a direction parallel to the axis of the branch artery andthe axis of the distal end of the guide catheter.

Another of the force vectors that acts on the guide catheter is ashearing force that tends to dislodge the distal end of the guidecatheter from the ostium of the branch artery in a directionperpendicular to the axis of the branch artery and the axis of thedistal end of the guide catheter. This force vector arises fromcurvature of the guide catheter near its distal end and the guide wirepushing on the curved portion of the guide catheter as the physicianapplies force to the guidewire. The coaxial guide catheter of thepresent invention assists in resisting both the axial forces and theshearing forces that tend to dislodge a guide catheter from the ostiumof a branch artery.

The system is deliverable using standard techniques utilizing currentlyavailable equipment. The present invention also allows atraumaticplacement within the coronary artery. Further, the invention isdeliverable through an existing hemostatic valve arrangement on a guidecatheter without preventing injections through existing Y adapters.Finally, the invention has an inner diameter acceptable for deliveringstandard coronary devices after it is placed in the blood vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of the coaxial guide catheter and atapered inner catheter in accordance with the present invention;

FIG. 2 is schematic depiction of the coaxial guide catheter and taperedinner catheter assembled in accordance with the present invention;

FIG. 3 is a plan view of a guide catheter, the coaxial guide catheter,and a treatment catheter in accordance with the present invention;

FIG. 4 is a sectional view of the coaxial guide catheter in accordancewith the present invention;

FIG. 5 is a cross sectional view of the coaxial guide catheter andtapered inner catheter in accordance with the present invention;

FIG. 6 is another cross sectional view of the coaxial guide catheter andtapered inner catheter in accordance with the present invention;

FIG. 7 is a schematic view of a guide catheter and a guidewire locatedin an aortic arch and a coronary artery and the guide catheter andguidewire in a second position depicted in phantom;

FIG. 8 is a schematic view of a guide catheter, a guidewire, a coaxialguide catheter in accordance with the present invention and a taperedinner catheter located in the aortic arch and coronary artery;

FIG. 9 is a schematic view of a guide catheter, a guidewire and acoaxial guide catheter in accordance with the present invention locatedin the aortic arch and coronary artery;

FIG. 10 is a flat pattern for making relief cuts in a curved rigidportion of the coaxial guide catheter in accordance with the presentinvention;

FIG. 11 is a detailed view taken from FIG. 10;

FIG. 12 is a plan view of the rigid portion in accordance with thepresent invention;

FIG. 13 is an elevational view of the rigid portion;

FIG. 14 is a sectional view of the rigid portion taken along sectionline 14-14 of FIG. 13; and

FIG. 15 is a sectional view of the rigid portion taken along sectionline 15-15 of FIG. 13.

FIG. 16 is a sectional view of the rigid portion taken along sectionline 16-16 of FIG. 13.

FIG. 17 is a plan view of a coaxial guide catheter having a longer railsegment and a tapered inner catheter in accordance with the presentinvention.

FIG. 18 is a plan view of the tapered inner catheter as depicted in theFIG. 17.

FIG. 19 is a cross-sectional view of the tapered inner catheter takenalong section lines 19-19 of FIG. 18.

FIG. 20 is a plan view of a coaxial guide catheter in accordance withthe present invention.

FIG. 21 is an elevational view of a coaxial guide catheter in accordancewith the present invention.

FIG. 22 is a cross-sectional view taken along section line 22-22 of FIG.21.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, coaxial guide catheter assembly 10 of thepresent invention generally includes coaxial guide catheter 12 andtapered inner catheter 14.

Coaxial guide catheter 12 generally includes tip portion 16, reinforcedportion 18, and rigid portion 20. The overall length of the coaxialguide catheter typically can be approximately 125 cm. This length shouldnot be considered limiting.

Tip portion 16 generally includes bump tip 22 and marker band 24. Bumptip 22 includes taper 26. Bump tip 24 is relatively flexible and may beformed, for example, from 4033 Pebax®. Bump tip 22 may be yellow oranother high visibility color for ease of handling.

Marker band 24 is formed of a radiopaque material such asplatinum/iridium alloy usually at a 90/10 ratio. Marker band 24 may besandwiched between an outer Pebax® material 28 and a PTFE liner 30.Outer Pebax® material 28 in this location may be formed of 5533 Pebax,for example.

Reinforced portion 18 includes braid or coil reinforcement 32. Braid orcoil reinforcement 32 may be formed of metal, plastic, graphite, orcomposite structures known to the art. Reinforced portion 18 may belined on the interior by PTFE liner 30 and covered on the exterior byPebax® material 28. Tip portion 16 and reinforced portion 18 togetherform a substantially cylindrical structure. Braid or coil reinforcement32 may extend approximately 20 to 30 cm. In one exemplary embodiment,braid or coiled portion has a length of approximately 32 to 36 cm.

Rigid portion 20 may be secured to braid or coil reinforcement by, forexample, welding or bonding. Rigid portion 20 may be formed from ahypotube or a section of stainless steel or Nitinol tubing. Othersubstantially rigid materials may be used as well. Rigid portion 20includes first full circumference portion 34, hemicylindrical portion36, arcuate portion 38, and second full circumference portion 40.

First full circumference portion 34 is joined to braid or coilreinforcement 32. First full circumference portion 34 extends for arelatively short distance, for example, 0.25 cm.

Hemicylindrical portion 36 desirably includes 40% to 70% of thecircumference of the tube. Hemicylindrical portion 36 may extend, forexample, approximately 20 to 75 cm in length.

Hemicylindrical portion 36 tapers into arcuate portion 38.

Arcuate portion 38 extends from 25% to 40% of the circumference of thetube. Arcuate portion 38 may extend linearly, for example, for about 15cm.

Arcuate portion 38 connects to second full circumference portion 40.Second full circumference portion 40 may extend for a short distance,for example, approximately 3 cm.

Tapered inner catheter 14 generally includes tapered inner catheter tip42 and cutout portion 44. Tapered inner catheter tip 42 tapers graduallyfrom the diameter of a guide wire to the diameter of tip portion 16.

Tapered inner catheter tip 42 includes tapered portion 46 at a distalend thereof, and straight portion 48. Both tapered portion 46 andstraight portion 48 are pierced by lumen 50.

Cutout portion 44 defines a concave track 52 along its length. Concavetrack 52 is continuous with lumen 50.

Tapered inner catheter 14 may also include clip 54 at a proximal endthereof to releasably join tapered inner catheter 14 to coaxial guidecatheter 12. Thus, tapered inner catheter 14 is keyed to coaxial guidecatheter 12.

Coaxial guide catheter 12 may include, starting at its distal end, afirst portion having a flexural modulus of about 13,000 PSI plus orminus 5000 PSI, a second portion having a flexural modulus of about29,000 PSI plus or minus 10,000 PSI, a third portion having a flexuralmodulus of about 49,000 PSI plus or minus 10,000 PSI and a fourthportion having a flexural modulus of about 107,000 PSI plus or minus20,000 PSI. Coaxial guide catheter 12 may be formed, for example, of4033 Pebax® at bump tip 22 for the first 0.1 cm. This portion mayfollowed by a section about three cm long of 5533 Pebax® that coversmarker band 24 and the distal portion of braid or coil reinforcement 32.Next may come an approximately five cm portion of 6333 Pebax® whichencloses part of braid or coil reinforcement 32 followed by anapproximately twenty seven cm portion of 7233 Pebax® covering the mostproximal portion of braid or coil reinforcement 32. Braid or coilreinforcement 32 is bonded to rigid portion 20 which may be formed fromstainless steel or a similar biocompatible material. Rigid portion 20may extend for approximately ninety cm and include first fullcircumference portion 34 (approximately 0.25 cm), hemicylindricalportion 36 (approximately seventy five cm), arcuate portion(approximately fifteen cm) and second full circumference portion(approximately three cm.) Rigid portion 20 may be formed from astainless steel or Nitinol hypo tube.

FIG. 7 depicts a typical guide catheter 56 passing through aortic arch58 into ostium 60 of coronary artery 62. FIG. 7 also depicts guidewire64 passing through the guide catheter 56 and into coronary artery 62.Located in coronary artery 62 is stenotic lesion 66. In a typicalprocedure, guidewire 64 is placed through the aortic arch 58 and intothe ostium 60 of the coronary artery. 62. The guide catheter 56 ispassed over guidewire 64 until distal end 68 of guide catheter 56 isseated in ostium 60 of coronary artery 62. Force is then applied to theguidewire 64 to push guidewire 64 past stenotic lesion 66 or anocclusive lesion (not shown). Once the guidewire 64 is pushed paststenotic lesion 66 or occlusive lesion (not shown), a treating catheterincluding a stent or balloon can be passed along the guidewire tostenotic lesion 66 or occlusive lesion (not shown). The lesion can thenbe treated.

As can be seen in phantom, in FIG. 7, the application of force toguidewire 64 can cause guide catheter 56 to dislodge from ostium 60 ofcoronary artery 62. This can occur in the case of a tough stenoticlesion 66 or occlusive lesion (not shown) when it is difficult to passthe guidewire 64 beyond the stenotic lesion 66 or occlusive lesion (notshown).

Referring the FIG. 8 coaxial guide catheter 12 is depicted as used withguide catheter 56, guidewire 64, and tapered inner catheter 14. Here,coaxial guide catheter 12 with tapered inner catheter 14 is passedthrough guide catheter 56 and over guidewire 64 into coronary artery 62after the guide catheter 56 has been placed in the ostium 60 of coronaryartery 62, as depicted in FIG. 7. Coaxial guide catheter 12, withtapered inner catheter 14, provide an inner support member for propertranslation over guidewire 64. Tapered inner catheter tip 42 provides adistal tapered transition from guidewire 64 to coaxial guide catheter12. Once coaxial guide catheter 12 is in place, tapered inner catheter14 is removed from the inside of coaxial guide catheter 12.

Coaxial guide catheter 12 is now ready to accept a treatment cathetersuch as a stent or balloon catheter. Referring to FIG. 9, thecombination of guide catheter 56 with coaxial guide catheter 12 insertedinto ostium 60 of coronary artery 62 provides improved distal anchoringof guide catheter 56 and coaxial guide catheter 12. The presence ofcoaxial guide catheter 12 within guide catheter 56 also provides stifferback up support than guide catheter 56 alone. The combination ofimproved distal anchoring and stiffening of the guide catheter56/coaxial guide catheter 12 combination provides additional back upsupport to resist dislodging of guide catheter 56 from ostium 60 whenforce is applied to guidewire 64 to pass through stenotic lesion 66 oranother lesion. In addition, the improved back up support assists in thepositioning of a treating catheter that may include a stent or balloon.

Referring to FIGS. 10 and 11, in some embodiments of coaxial guidecatheter 12, rigid portion 20 may be perforated by relief cuts 70.Relief cuts 70 may be classed into first group 72 and second group 74.

First group 72 may be located near to the juncture between rigid portion20 and reinforced portion 18. First group 72 of relief cuts 70 arerelatively closely spaced. For example, first group 72 of relief cuts 70may be spaced approximately 0.010 inches apart. First group 72 of reliefcuts 70 extends for a relatively short distance, for example,approximately 2 inches.

Second group 74 of relief cuts 70 may extend for a relatively longdistance, for example, approximately 30-35 inches. Second group 74 ofrelief cuts 70 are spaced farther apart than first group 72. Forexample, relief cuts 70 of second group 74 may be spaced approximately0.020 inches between cuts. Referring particularly to FIG. 11, reliefcuts 70 may include single cuts 76 and double cuts 78. Single cuts 76may include an individual linear cut, as can be seen in FIG. 11. Doublecuts 78 may include two linear cuts along a single line but separated bya short section of uncut structure. Typically, single cuts 76 and doublecuts 78 are alternated along the length of rigid portion 20. Generally,the overall length of single cut 76 may be less than the overall lengthof two double cuts 78.

In an embodiment depicted in FIGS. 12-15, rigid portion includes fullcircumference portion 80, greater than 180° portion 82, and less than180° portion 84. Greater than 180° portion 82 may, for example, includestructure forming approximately 300° of the circumference of thecylinder. Less than 180° portion may include, for example, structureforming approximately 90° of the circumference of a cylinder. Greaterthan 180° portion 82 may extend approximately 22-25 inches. Greater than180° portion 82 holds tapered inner catheter 14 within rigid portion 20.

When tapered inner catheter is inserted into coaxial guide catheter 12greater than 180° portion 82 grips tapered inner catheter 14 which isexposed through the opening in greater than 180° portion 82. Thus, theoverall structure of tapered inner catheter 14 along with greater than180° portion 82 is substantially cylindrical. Accordingly, when insertedthrough a guide catheter 56 having a Touhey-Borst style adapter, theTouhey-Borst style adapter can still seal around rigid portion 20 andenclosed inner tapered catheter 14.

Referring to FIG. 16, another embodiment of coaxial guide catheterassembly 10 includes coaxial guide catheter 12 and tapered innercatheter 14. Tapered inner catheter 14 is keyed to coaxial guidecatheter 12 at hub 86.

Referring to FIGS. 17 and 18, tapered inner catheter 14 generallyincludes connector hub 88 and catheter tube 90.

Connector hub 88 generally includes connector portion 92, grip portion94 and joining portion 96. Connector hub 88 defines funnel portion 98therein.

Catheter tube 90 generally includes straight portion 100, taperedportion 102 and marker band tip 104. Catheter tube 90 is joined toconnector hub 88 at joining portion 96. Tapered inner catheter 14 may beformed in whole or in part from low-density polyethylene plastic, forexample. Other suitable materials known to the catheter arts may be usedas well.

Grip portion 94 desirably includes gripping ears 106. Gripping ears 106may extend outwardly from grip portion 94 substantially radially and beshaped for convenient gripping by a physician.

Referring to FIGS. 19 through 21, in this embodiment, coaxial guidecatheter 12 includes interrupted hub 108, hemi-tube portion 110, braidedportion 112 and tip portion 114.

Interrupted hub 108 defines an opening 116, along a side thereof.Interrupted hub 108 may be substantially C-shaped or U-shaped in crosssection. Opening 116 is sized so that tapered inner catheter 14 may bepassed readily therethrough in a direction perpendicular to the longaxes of both interrupted hub 108 and tapered inner catheter 14.Hemi-tube portion 110 is immediately distal to interrupted hub 108.Hemi-tube portion 110 may be formed, for example, from a metal hypo tubeforming approximately 50% of the circumference of a cylinder. Hemi-tubeportion 110 is aligned so that opening 116 of interrupted hub 108 iscoextensive with opening 118 of hemi-tube portion 110. Hemi-tube portion110 is joined to braided portion 112, for example, by adhesive, bondingor welding. The location where hemi-tube portion 110 and braided portion112 join defines the entire circumference of a cylinder.

Braided portion 112 may be reinforced by a coil or braid, 120. Coil orbraid 120 may be formed of metal or another suitable reinforcingmaterial.

Tip portion 114 is generally not reinforced and is substantially soft.Tip portion 114 is similarly structured to tapered inner catheter tip42. Tip portion 114 may include a radiopaque marker band 24.

Beginning at the distal end of coaxial guide catheter 12, tip portion114 may be formed substantially of, for example, 2533 Pebax® This may befollowed by a section of 3533 Pebax®, then by a section of 5533 Pebax®,then by a further section of 7233 Pebax®. These Pebax® portions may allincorporate, for example, about 20% barium sulfate (BaSO₄).

In one embodiment, tip portion 114 and braided portion 112 may have anoverall length together of approximately one hundred nine centimeters.Hemi-tube portion 110 and interrupted hub 108 may together have anoverall length of approximately eighteen centimeters.

In this embodiment, coaxial guide catheter 12 may be lined with a PTFEliner 122.

In operation, a guide catheter 56 is inserted into a major blood vesselin the body such as aortic arch 58 over guidewire 64 and the distal end68 of guide catheter 56 is brought into proximity of ostium 60 of asmaller branch blood vessel, such as coronary artery 62, that it isdesired to enter. Coaxial guide catheter 12, with tapered inner catheter14, is inserted through guide catheter 56 and over guidewire 64. Guidecatheter 56, guidewire 64, coaxial guide catheter 12, and tapered innercatheter 14 are manipulated to insert tapered inner catheter tip 42 intothe ostium 60 of the blood vessel that branches off from the major bloodvessel. The bump tip 22 of coaxial guide catheter 12 is inserted withtapered inner catheter tip 42 well into ostium 60 of coronary artery 62or other blood vessel until bump tip 22 of coaxial guide catheter 12achieves a deep seated position. Tapered inner catheter 14 is thenwithdrawn from the lumen of coaxial guide catheter 12. An interventionalcardiology treatment device such as a catheter bearing a stent or aballoon (not shown) is then inserted through the lumen of coaxial guidecatheter 12 which remains inside guide catheter 56.

When the interventional cardiology device reaches a stenosis or blockagein coronary artery 62 or another branch blood vessel, force may beapplied to the interventional cardiology device catheter whilereinforced portion 18 and rigid portion 20 of coaxial guide catheter 12provide back up support. The back force that would tend to dislodge bumptip 22 from a deep seated position in the ostium in the branch bloodvessel is transferred through reinforced portion 18 to rigid portion 20of coaxial guide catheter 12. A physician may apply a force to theproximal end of the coaxial guide catheter 12 to resist dislodging ofbump tip 22 from the ostium of the branch artery.

One advantage of the present invention over prior art approaches is thatthe present invention does not interfere the injection of fluids via theY-adapter of guide catheter 56 as does the use of a smaller catheterwithin a larger catheter.

The present invention may be embodied in other specific forms withoutdeparting from the spirit of the essential attributes thereof;therefore, the illustrated embodiments should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

1. A method of providing backup support for an interventional cardiologydevice for use in the coronary vasculature, the interventionalcardiology device being adapted to be passed through a guide catheter,the method comprising: inserting the guide catheter into the first bloodvessel, the guide catheter having a first lumen and a distal end;positioning the distal end of the guide catheter in a second bloodvessel that branches off from the first blood vessel; inserting acoaxial guide catheter over the guidewire and into the first lumen ofthe guide catheter, the coaxial guide catheter having a second lumen anda flexible distal tip portion, a reinforced portion proximal to thedistal tip portion, and a substantially rigid portion proximal to thereinforced portion, the substantially rigid portion having an openingalong a side thereof, advancing the distal tip portion of the coaxialguide catheter into the second blood vessel such that the flexibledistal tip portion and at least a portion of the reinforced portionextend out of the distal end of the guide catheter and into the secondblood vessel; and inserting the interventional cardiology device throughthe lumen of the coaxial guide catheter and into contact with or past alesion in the second blood vessel.
 2. The method as claimed in claim 1,further comprising applying a force to a proximal portion of the coaxialguide catheter such that the distal tip portion of the coaxial guidecatheter remains seated in the second blood vessel in response to anopposing backward force exerted by the interventional cardiology device.3. The method as claimed in claim 1, further comprising: keying thetapered inner catheter to the coaxial guide catheter at a proximalportion thereof; inserting a guidewire having a tip into a first bloodvessel; and inserting the tip of the guidewire into a second bloodvessel that branches off of the first blood vessel.
 4. The method asclaimed in claim 1, further comprising selecting the substantially rigidportion of the coaxial guide catheter such that it comprises acylindrical portion and a partially cylindrical portion defining theopening along a side thereof.
 5. The method as claimed in claim 1,further comprising selecting the guide catheter to further comprise aY-adapter and the method further comprising injecting a fluid throughthe Y-adapter into the second lumen.
 6. The method as claimed in claim1, further comprising inserting a guidewire having a tip into a firstblood vessel; and inserting the tip of the guidewire into a second bloodvessel that branches off of the first blood vessel.
 7. The method asclaimed in claim 6, further comprising placing a tapered inner catheterinside the second lumen of the coaxial guide catheter, the tapered innercatheter including a tapered distal portion, the tapered distal portionbeing positioned to extend beyond the distal tip of the coaxial guidecatheter; removing the tapered inner catheter from the coaxial guidecatheter; and removing the guidewire from the coaxial guide catheter. 8.A device to be passed through guide catheter having a first lumen, foruse with interventional cardiology devices that are insertable into abranch artery that branches off from a first artery, the devicecomprising: an elongate structure defining a second lumen and beingsized to pass through the first lumen of the guide catheter, theelongate structure including a flexible distal tip portion; a reinforcedportion proximal to the flexible distal tip portion; and a substantiallyrigid portion proximal to the reinforced portion, the substantiallyrigid portion including a partially cylindrical portion defining anopening along a side thereof, the opening extending substantially alongat least a portion of a length of the rigid portion; such that when thedevice is extended through the lumen of the guide catheter and beyondthe distal end of the guide catheter and inserted into the branchartery, the device assists in resisting axial and shear forces exertedby an interventional cardiology device passed through the second lumenand beyond the flexible distal tip portion that would otherwise tend todislodge the guide catheter from the branch artery.
 9. The device asclaimed in claim 8, further comprising: a radiopaque marker proximatethe distal tip; wherein the reinforced portion comprises a braid or coilformed of metal; and wherein the substantially rigid portion defines aplurality of relief cuts therein, the relief cuts controlling therigidity of at least a portion of the substantially rigid portion. 10.The device as claimed in claim 8, further comprising a tapered innercatheter proportioned to pass through the second lumen and to extendoutwardly from the flexible distal tip, the tapered inner catheterdefining a third lumen through which the tapered inner catheter may bepassed over a guidewire to facilitate insertion of the device, thetapered inner catheter being removable prior to insertion of theinterventional cardiology device.
 11. The device as claimed in claim 10,wherein the tapered inner catheter has a first portion and a secondportion, the first portion defining a lumen therethrough and the secondportion defining a concave track.
 12. The device as claimed in claim 8,wherein portions of the device intended for passage into the guidecatheter have a size selected from a group consisting of about eightFrench, about seven French and about six French.
 13. The device asclaimed in claim 8, further comprising, starting at a distal end, apolymer exterior having a first portion having a first flexural modulus,a second portion having a second flexural modulus greater than the firstflexural modulus, a third portion having a third flexural modulusgreater than the second flexural modulus and a fourth portion having afourth flexural modulus greater than the third flexural modulus.
 14. Thedevice as claimed in claim 13, in which the first flexural modulus isabout 13,000 PSI plus or minus 5000 PSI, the second flexural modulus isabout 29,000 PSI plus or minus 10,000 PSI, the third portion flexuralmodulus is about 49,000 PSI plus or minus 10,000 PSI and the fourthflexural modulus is about 107,000 PSI plus or minus 20,000 PSI.
 15. Thedevice as claimed in claim 13, in which the first portion is about 0.1cm in length, the second portion is about three cm in length, the thirdportion is about five cm in length and the fourth portion is abouttwenty seven cm in length.
 16. The device as claimed in claim 10,wherein the coaxial guide catheter and the tapered inner catheter arekeyed at their respective distal ends to allow releasable connection ofthe coaxial guide catheter and the tapered inner catheter to each other.17. A kit for performing interventional cardiology procedures thatinclude insertion of a treatment catheter into a blood vessel, the kitcomprising: a guide catheter having a first lumen; a coaxial guidecatheter comprising an elongate structure defining a second lumen andbeing sized to pass through the first lumen of the guide catheter, thecoaxial guide catheter including: a flexible distal tip portion; areinforced portion proximal to the flexible distal tip portion; and asubstantially rigid portion proximal to the reinforced portion, thesubstantially rigid portion including a short cylindrical portion and apartially cylindrical portion defining an opening along a side thereof,the opening extending substantially along a majority of a length of therigid portion.
 18. The kit as claimed in claim 17, further comprising atapered inner catheter sized to fit within the second lumen having atapered distal tip and defining a third lumen through which a guidewiremay be passed.
 19. The kit as claimed in claim 17, the coaxial guidecatheter further comprising, starting at a distal end, a polymerexterior having a first portion having a first flexural modulus, asecond portion having a second flexural modulus greater than the firstflexural modulus, a third portion having a third flexural modulusgreater than the second flexural modulus and a fourth portion having afourth flexural modulus greater than the third flexural modulus.
 20. Thekit as claimed in claim 19, in which the first flexural modulus is about13,000 PSI plus or minus 5000 PSI, the second flexural modulus is about29,000 PSI plus or minus 10,000 PSI, the third portion flexural modulusis about 49,000 PSI plus or minus 10,000 PSI and the fourth flexuralmodulus is about 107,000 PSI plus or minus 20,000 PSI.